Various industrial processes emit emissions containing undesirable pollutants like NOx, CO, VOCs and HAPs. These harmful pollutants may need to be removed from the flue gas before releasing into the atmosphere to meet the Environmental Protection Agency (EPA) requirements. Current technologies enabling industries to remove the pollutants include thermal oxidation (direct fired, recuperative or regenerative) and selective catalytic reduction.
Existing thermal oxidation technologies are limited to the removal of CO, VOCs and HAPs by heating the flue gas to a temperature greater than 1400 deg. F. Direct fired thermal oxidation has no heat recovery. Recuperative thermal oxidation may recover 60-80% of the heat required to heat the flue gas to a temperature greater than 1400 deg. F. Regenerative thermal oxidation may recover 85-95% of the heat required to heat the flue gas to a temperature greater than 1400 deg. F.
Existing selective catalytic reduction technologies are believed to be limited to the removal of NOx by either entry into the process system where the temperature is between 500 to 700 deg. F or heating the flue gas to a temperature between 500 to 700 deg. F. These technologies do not appear to be capable of removing NOx efficiently at a flue gas temperature of less than 480 deg. F.
Other potential limitations of the current selective catalytic reduction technologies include, but are not limited to: (1) issues of incorporation into systems where space is constrained close to the temperature zone between 480 to 700 deg. F; (2) revamps of existing systems are limited where turnaround times are not achievable unless the NOx removal product is only by a standalone tie-in; (3) multiple process streams resulting in fluctuating flue gas temperature from ambient to less than 480 deg. F.; and (4) catalyst plugging by the particulate matter in the flue gas.